Various ion-exchange processes have been developed to modify glass surfaces. For example, U.S. Pat. No. 3,844,754 discloses a process for strengthening a glass article by forming a solid layer of an alkali metal salt on a surface of the glass, and then heating the glass article and the solid layer at an elevated temperature to carry out an exchange of ions. The alkali metal salt must contain an alkali metal carbonate, and the glass article may be heated to a suitably elevated temperature by passing the glass article through an annealing lehr.
A general object, in accordance with one aspect of the disclosure, is to provide a surface treatment process for reducing light reflection from a glass container, without reducing light transmission through the glass container (i.e., without reducing the clarity of the container). A general object, in accordance with another aspect of the disclosure, is to provide a surface treatment process for strengthening a glass container. A general object, in accordance with yet another aspect of the disclosure, is to provide a surface treatment process for a glass container, which can be used to prepare the glass container for the subsequent application of one or more cold-end coatings.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.
In accordance with an aspect of the disclosure, there is provided a surface treatment process for a glass container comprising: contacting at least a portion of the glass container with an aqueous electrolyte solution, and then heating the glass container with the aqueous electrolyte solution to a temperature between 70 degrees Celsius and 100 degrees Celsius for a time sufficient to exchange alkali metal ions in a surface portion of the glass container with alkali metal ions in the electrolyte solution. The aqueous electrolyte solution comprises salts of at least one group IA alkali metal and has a salt mass fraction in the range of 10-50%.
In accordance with another aspect of the disclosure, there is provided a process for producing a soda-lime-silica glass container including the steps of: (a) forming the glass container; (b) annealing the glass container; (c) immersing at least a portion of the glass container in an aqueous electrolyte solution containing salts of a group IA alkali metal; and then (d) applying a cold-end coating to an exterior surface of the glass container. The aqueous electrolyte solution has a temperature between 70 degrees Celsius and 100 degrees Celsius and a salt mass fraction in the range of 10-50%. The glass container is immersed in the aqueous electrolyte solution to exchange ions in a surface portion of the glass container with at least a portion of the alkali metal ions in the electrolyte solution.
In accordance with yet another aspect of the disclosure, there is provided a surface treatment process for a silica-based glass container which comprises exchangeable metal ions of at least one of sodium (Na+) and calcium (Ca2+). The surface treatment process includes: contacting at least a portion of the glass container with an aqueous electrolyte solution comprising group IA alkali metal ions for a time sufficient to exchange at least a portion of the exchangeable metal ions in the silica-based glass container with at least a portion of the group IA alkali metal ions in the aqueous electrolyte solution. The aqueous electrolyte solution has a temperature between 70 degrees Celsius and 100 degrees Celsius and comprises group IA alkali metal ions that have ionic radii larger than that of sodium (Na+) or calcium (Ca2+) ions.